I The primary long-term objective of this research is to understand the role of AKT-signaling cross-talk with the estrogen receptor (ER) in the control of cell survival and in the development of anti-estrogen resistance. We hypothesize that the AKT pathway functions to target and phosphorylate the p160 coactivator GRIP and ER proteins leading to regulation of CoA-recruitment, receptor-activation and gene expression. We further hypothesize that convergence of the AKT and estrogen signaling at the ER-CoA-transcriptional level is critical in the regulation of cell survival and influences selective estrogen receptor modulator (SERM) activity in hormone dependent cell systems such as breast carcinoma. The Specific Aims are proposed to 1) Determine the mechanisms of AKT-ER cross-talk by examining specific targeting, phosphorylation and activation of ER-AF2 and/or the p160 CoA GRIP by AKT and 2) Determine the physiological relevance of this cross-talk by examining effects of AKT-ER-CoA on the regulation of endogenous estrogen-responsive genes, alteration of SERM-activity and gene expression, and long-term cell survival. Specific Aim #1, To determine the role of AKT targeting and phosphorylation of ER-AF2 as a mechanism for cross-talk. We propose to determine if the ER-AF2 targeting occurs through direct phosphorylation by AKT and the role of specific phosphorylation sites in AKT-ER cross-talk. Specific Aim #2, To implicate AKT regulation of p160 coactivator-(GRIP) phosphorylation as a mechanism for activation of and recruitment to estrogen receptors. Studies will determine if AKT phosphorylates and activates GRIP though specific targeting of the GRIP-NRID (nuclear receptor interaction domain) or GRIP-AD2 (activation domain-2) as mechanisms for AKT regulation of GRIP in control of ER transcription. Specific Aim #3, To determine the requirement for GRIP phosphorylation/function in AKT-mediated regulation of ER-dependent cell survival, gene expression and SERM activity. In this aim we will determine the role for specific AKT induced ER-CoA recruitment/activation in the regulation of cell survival gene expression (Bcl-2) and the influence of AKT-ER-CoA cross-talk on SERM activity. These studies will also determine if the mechanisms for AKT-phosphorylation of ER or GRIP from above are critical in the AKT-ER mediated regulation of cell survival. It is expected as a whole that this proposal will establish the mechanisms used by the PI3K-AKT cascade to target the ER and the subsequent components of the ER transcription complex required for potentiation of activity by this pathway. This cross-talk and the mechanisms identified will be used to establish the biological relevancy of the Dathway in terms of cell survival and altered SERM activity,